One of the young guys that works for me is going to school at IL state. He will live off campus in a rented house and wants to bring his AR with him.

Can he do this without any legal issues?

IANAL

There are no statewide restrictions on owing and possessing an AR in IL.

Being off campus, I would assume university relevant restrictions, if any,  would not apply

If there are no local ordinances and nothing about firearms in his lease, I'd think he's OK.

Perhaps someone with more knowledge of the area  will be along to provide greater insight.

ETA: just noticed title indicated he is an IN resident, but can't think of what that impact that would have. In spite of being in IL for school majority of year, I assume IN residency is maintained.

Non-residents

A non-resident is permitted to possess a firearm without a FOID if it is unloaded and enclosed in a case, or if the nonresident is:

• Hunting and has a non-resident hunting license, while in an area where hunting is permitted.

• On a target range recognized by the Department of State Police.

• At a gun show recognized by the Department of State Police.

• Currently licensed or registered to possess a firearm in his state of residence.