This paper presents an implemented, psychologically plausible parsing model for Government Binding theory grammars. I make use of two main ideas: (1) a generalization of the licensing relations of [Abney, 1986] allows for the direct encoding of certain principles of grammar (. Theta Criterion, Case Filter) which drive structure building; (2) the working space of the parser is constrained to the domain determined by a Tree Adjoining Grammar elementary tree. All dependencies and constraints are locaiized within this bounded structure. .