NEW BRUNSWICK, N.J.—Gov. Chris Christie signed legislation Wednesday to reorganize three state universities, one of the largest restructurings of New Jersey's colleges in decades and a hard-fought political victory for the Republican governor.

Now that it's signed, the New Jersey Medical and Health Sciences Education Restructuring Act clears the way for merging Rutgers University with the Newark and New Brunswick campuses of the University of Medicine and Dentistry of New Jersey, the state's public medical school.

UMDNJ's...