In ancient times traitors were given capital punishment.
Tips
usage
处 here is read chǔ (3rd tone, 'to handle / sentence'), not chù (4th tone, 'place'). The construction 处以 ... 刑 ('sentence to ... punishment') is common in legal language: 处以死刑 (death penalty), 处以罚款 (fine).
register
Formal/legal. In modern Japanese-influenced fiction (anime, manga 处刑シーン), 处刑 specifically connotes execution; in legal Chinese it means 'sentence' more broadly.
