Sentence:  It was reasonably clear upon the argument submitted in the Court of Session that, at the time when the Act came into force, it was regarded by <WSD>contemporanea expositio</WSD> as applying to the Crown, but any doubt which might have existed was set ... 
Meaning of the word marked with <WSD> tags:  The doctrine that the legal opinions of the time a document was written should be used to interpret laws in preference to more modern formulations.