The first assertion of the freedom of association of Argentina can be found in Part I, Chapter 1, Article 14 of the Constitution of the Argentine Nation of 1853. The 1853 Constitution as amended to 1957 specifies association rights with reference to labor unions and trade unions. This language remains in the Constitution as amended to 1994.

References:

1853 Argentina Constitution:French translation of the original Constitution of 1853 780 (2010) Chapter I: https://heinonline-org.proxygw.wrlc.org/HOL/Page?collection=cow&handle=hein.cow/zzar0007&id=2&men_tab=srchresults

1853 Argentina Constitution as amended to 1957: English text of the Constitution of 1853 consolidated as amended to 1957. 3 (2011) First Part: Declarations, Rights, and Guarantees: https://heinonline-org.proxygw.wrlc.org/HOL/Page?collection=cow&handle=hein.cow/zzar0015&id=7&men_tab=srchresults#

Argentina Constitution as of 1994: http://www.biblioteca.jus.gov.ar/Argentina-Constitution.pdf