See perhaps Article 217 of TFEU:

> The Union may conclude with one or more third countries or international organisations agreements establishing an association involving reciprocal rights and obligations, common action and special procedure.

* https://eur-lex.europa.eu/eli/treaty/tfeu_2012/art_217/oj/en...

An article going into it:

> Association is already an established form of EU external relations. The Euro-Mediterranean Association Agreement with Morocco entered into force on March 1, 2000. The EU–Ukraine Association Agreement entered fully into force on September 1, 2017. Their substantive commitments and institutional structures differ, reflecting the relationships negotiated by the respective parties (Council of the European Union, 2000; European External Action Service, 2017).

> Article 217 does not prescribe a uniform degree of integration. Depending on its provisions, an association agreement may establish economic commitments, regulatory cooperation, joint institutions, and procedures for implementing shared objectives. The associated country's rights arise from the agreement rather than from a standardized legal status conferred by Article 217 itself.

* https://www.diplomacyandlaw.com/post/canada-eu-associate-mem... §3