No, with two exceptions. One is if you committed a serious offense like killing a Christian or going over to the Muslims. You would be officially expelled from the Order—straight into the jail of one of the Order's fortresses, where you probably wouldn't live very long. The other was if you got leprosy. read more
There were also Templar associates such as confratres or land tenants, who could leave. And yes, these people often identified as (and were identified by the Order as) Templars. Not all of them were monks. read more
The Crusades and the Knights Templar The Knights Templar were the elite fighting force of their day, highly trained, well-equipped and highly motivated; one of the tenets of their religious order was that they were forbidden from retreating in battle, unless outnumbered three to one, and even then only by order of their commander, or if the Templar flag went down. read more