Looking on the internet deeply has found these results:

on the campus is the most popular phrase on the web.

in the campus 1594,000 results on the web	on the campus 132,900,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
Jun 2, 2005 ... ... area, grounds and buildings and therefore it is correct to say 'on'. Click to expand... So would that make it incorrect to say "in the campus"? His name is chiefly associated with the quarrels between Lothair and Louis the Pious, in which he espoused the cause of the former, for whom, in the Campus�... Jul 30, 2009 ... Hey everyone. How would you say this: "I'm on the campus" "I'm on campus" "I'm in campus" "I'm in the campus" I've heard people saying both�... Jun 10, 2015 ... Everything counts in the campus visit. Atmosphere, location, even food can deter potential applicants. E Mail�...	This was two nights ago on the campus of Gateway University. Something that no one on the campus would understand. Freemont College officials have said that counseling will be available on the campus... I just don't want to be the only common In 1939, on the campus of a Midwestern university... not far from Columbus, Ohio, there was a brilliant young student. law wife on the campus. I'm scanning WiFi networks on the campus. Sir, I'm here on the campus.

in the campus

1594,000 results on the web

on the campus

132,900,000 results on the web

More popular!

Jun 2, 2005 ... ... area, grounds and buildings and therefore it is correct to say 'on'. Click to expand... So would that make it incorrect to say "in the campus"?
His name is chiefly associated with the quarrels between Lothair and Louis the Pious, in which he espoused the cause of the former, for whom, in the Campus�...
Jul 30, 2009 ... Hey everyone. How would you say this: "I'm on the campus" "I'm on campus" "I'm in campus" "I'm in the campus" I've heard people saying both�...
Jun 10, 2015 ... Everything counts in the campus visit. Atmosphere, location, even food can deter potential applicants. E
Mail�...

This was two nights ago on the campus of Gateway University.
Something that no one on the campus would understand.
Freemont College officials have said that counseling will be available on the campus...
I just don't want to be the only common
In 1939, on the campus of a Midwestern university... not far from Columbus, Ohio, there was a brilliant young student.
law wife on the campus.
I'm scanning WiFi networks on the campus.
Sir, I'm here on the campus.