The University of Calgary and its student union are locked in a legal battle over who owns MacEwan Hall — a campus building that houses a food court, student services and concert venue.

The students' union served the university with a lawsuit on Wednesday claiming it owns 55 per cent of the building, according to the statement of claim filed in a Calgary court.

At issue is the share of revenue that flows from the tenants in the building, as well as decisions about how Mac Hall — as the building is commonly known — is run.

"In the past couple of years ... [the university has] repeatedly said that any future deal would be us as tenants and them as owners, and that we would be excluded from a large amount of the revenue,... and that we would not be able to decide what the space is used for," said student union president Levi Nilson.

"We've been given the opportunity to do that for decades and Mac Hall is the heart of student campus because of it," he added.

The union says it has poured more than $19 million into construction and renovations costs since 1969, and that it has documents going back 60 years that prove it owns 55 per cent of the building.

It also claims the university has threatened to evict it from the building.

The university would only say that it is "extremely disappointed" with the legal action, and issued the following statement.

"The university's priority has always been to create a great experience for all students on campus and we want Mac Hall to continue to be a focal point of that experience," said lead negotiator Dru Marshall, provost and vice-president (academic).

The university said it would provide no further comment while the matter is before the courts.