In enterprise architecture governance is used in the sense of corporate IT compliance, in the sense of Sarbanes-Oxley or Basil II. IT systems must comply with various laws, policies, plans, standards and higher level architecture. Enterprise architecture artifacts and system engineering plans are reviewed by governance processes. Those processes vary by organization.
Conversely actual systems are checked for compliance via testing.
"If you do anything long enough, you eventually get good at it." MK