Five things the texts say

The Parties must ensure that persons “may circulate between Gibraltar and the Member States applying the Schengen acquis in full without border checks being carried out, without prejudice to the provisions on sea borders in Annex VI of the Schengen Borders Code” (Article 30(1)). Where there is a serious threat to public policy, public health or internal security, the EU countries applying the Schengen rules in full or the UK, for Gibraltar, “may exceptionally reinstate border control” for up to 10 days, which may be prolonged by 20 days and then by periods of one month, up to six months in all; this may be done only as a last resort and not beyond what is strictly necessary (Article 30(2)). As a general rule, Spanish officers in the airport immigration booths may be in uniform (Arrangement 4, paragraph 2.1.4(a)). Spanish officers carrying out continued surveillance in Gibraltar under Article 55 may carry service weapons during the surveillance, “save where specifically otherwise decided by the requested Participant” (Arrangement 5, paragraph 3.4(c); the arrangement does not define that term). Spanish officers in a pursuit under Article 56 may carry service weapons (paragraph 6.4(d)). In both cases their use is prohibited “save in cases of legitimate self-defence”. Spanish customs officers on a joint visit (Arrangement 7, joint visits, paragraph 11.8) and at the port (Arrangement 7, travellers, paragraph 6.4) are in civilian clothes, suitably identified, and carry no service weapons; at the port, the authorities of the UK, for Gibraltar, escort them (travellers, paragraph 6.4).

Our reading of “requested Participant”: the side into whose territory the surveillance continues.

A person resident in Gibraltar (Article 26(j)) who does not meet the other Schengen entry conditions “shall in any event not be prevented from crossing” the border crossing points to enter Gibraltar (Article 43(2)). If Spain considers that a resident “constitutes a sufficiently serious threat to public policy or internal security, public health or its international relations”, it may decide that the person is prohibited from leaving Gibraltar to travel into the EU countries that apply the Schengen rules in full. It notifies the authorities of the UK, for Gibraltar, giving the reasons and the means of appeal “before a national court of the Kingdom of Spain”; an appeal need not have suspensive effect (Article 46(2)). Article 46 does not apply to the persons listed in Article 46(4). Before the UK, for Gibraltar, issues or renews a residence permit, it notifies Spain. Within 28 days Spain may object, where the applicant is considered a threat to public policy, internal security, public health or the international relations of an EU country, and it may extend the 28 days by up to 14 days (Article 50(2) to (4)). These steps do not apply to the persons listed in Article 50(12), and Article 50 applies only until the Visa Information System starts operating (Article 50(10)), after which Article 51 applies.

Information about people and businesses in Gibraltar reaches Spain or the EU by separate routes, each under its own rule. Examples: notice of residence permits (Article 50(2)); a risk assessment on residents at least every three months (Article 46(1)); each year, tax information on people who work in Gibraltar and live in Spain within a radius of 80 km of Gibraltar (2019 tax agreement, Article 3(5)(a) and (15)(b)(i)); and access for the competent authorities within the EU to “any relevant IT systems” that Gibraltar's competent authorities use for the application of the customs Title (Article 251(2)). Some information also comes back to Gibraltar (2019 tax agreement, Article 3(10)). Under Article 31, “Under this Agreement, the competent authorities of the United Kingdom, in respect of Gibraltar, shall have no access to information systems and databases established on the basis of Union law”; Article 251(1) gives them access to the EU's transit system through Spain's IT system, for the purposes of applying Articles 242, 245, 247 and 248.

For the EU acts that Article 19 covers, the treaty “shall be considered terminated” if the UK, for Gibraltar, notifies that it does not accept a subsequent EU act, does not notify within the 30 days of Article 19(3), or does not inform the EU within six weeks of the act's entry into force that it has implemented it, unless the Cooperation Council “decides otherwise within 90 days”; termination takes effect three months after the end of the 90 days (Article 19(5)). The Cooperation Council “shall adopt decisions and make recommendations by mutual consent” (Article 24(2)). Either Party may end the treaty by written notice, effective on the first day of the twelfth month after the notice (Article 334). After the evaluation referred to in Article 65, the EU, “including at the request of the Kingdom of Spain”, and the UK “may terminate this Agreement by written notification through diplomatic channels”, and the treaty ceases to be in force on the first day of the twelfth month following the date of notification (Article 66(1)). If one side considers that the other has seriously and substantially failed to meet the essential elements (Articles 8(1), 9(1) and 10(1)), it “may decide to terminate or suspend the operation of this Agreement or any supplementing agreement in whole or in part”; before doing so it “shall request that the Cooperation Council meet immediately with a view to seeking a timely and mutually agreeable solution”, and if none is found “within 30 days from the date of the request to the Cooperation Council” it “may take the measures” (Article 16(2) and (3)). The first sentence of Article 16(5) reads: “The Parties consider that, for a situation to constitute a serious and substantial failure to fulfil any of the obligations described as essential elements in paragraph 1, its gravity and nature would have to be of an exceptional sort that threatens peace and security or that has international repercussions.” The treaty does not prejudice the legal positions of the UK and Spain on sovereignty and jurisdiction (Article 2).

The UK, for Gibraltar, made no notification under Article 122(2) (Legal Notice 237 of 2026, in operation from 23 July 2026: “makes no notification in relation to this provision”). Surrender on an arrest warrant may not be refused on the ground that the requested person is a national of the UK (Article 122(1)). A notification may next be made “during the three months prior to the fourth anniversary of the entry into force of this Agreement”, provided the conditions in Article 122(2) are met at that time (Article 149). Article 336(4) reads “entry into force” as the date from which the treaty is provisionally applied; that date is 15 July 2026 (European Commission press release IP/26/1609), so the window is the three months before 15 July 2030.