Case filter

In syntax, a case filter is a filter which requires an (overtly realized) NP argument to be case marked, or be associated with a case position.

Examples
This filter rules out (a, b). No case is assigned to the subject position of the complement of seems; only by moving to the subject position of the matrix clause can John satisfy the case filter: it is assigned case there.

a * it seems [ John to be angry ]

b  John seems [ ti to be angry ]

Comment
More recently, the case filter has been reduced to the visibility condition.

Link
Utrecht Lexicon of Linguistics

Other languages
German Kasusfilter