• 拘こうる（かかわる） — to be concerned with; to be particular about
• 拘束こうそく — restraint; confinement; restriction
• 拘留こうりゅう — detention; custody
• 拘置こうち — confinement; incarceration
• 拘泥こうでい — being obsessed or stuck on small details

The hand radical 扌 shows physical action — reaching, holding, or seizing. In 拘, that hand extends to grip or stop something. That’s why it means “to detain,” “to arrest,” or even “to be caught up in” an idea or detail.