Decline is a synonym of Vary. Vary is a synonym of Depart. Depart is a synonym of Abandon. Abandon is the opposite of Maintain. 
League is a type of Organization. Institution is a type of Organization. 
Decline <--Synonym--> Vary <--Synonym--> Depart <--Synonym--> Abandon <--Antonym--> Maintain 
League --IsA--> Organization <--IsA-- Institution 