some contracts are for a fixed-term period of, say, one to two years as a graduate, 'rotating' lawyer. some contracts are of an indefinite term.
of course it's possible to leave a graduate job after one year. whether or not there are consequences tied to your departure depends on the circumstances.
Thanks for the reply. I am hoping to leave a graduate program after 1 year to move overseas, so I am just trying to work out the technicalities of doing so.