Which action can lead to a lawsuit for violating an individual's constitutional rights?

The action that can lead to a lawsuit for violating an individual's constitutional rights is false arrest of a person. False arrest occurs when a person is detained or restrained without legal justification or probable cause, infringing on their Fourth Amendment right against unreasonable seizures. This legal concept allows individuals to seek redress in court if they believe that law enforcement has improperly detained them without proper legal grounds.

In contrast, providing adequate legal counsel is a constitutional requirement under the Sixth Amendment and does not itself constitute a violation of rights. Routine traffic stops, while they can raise issues of reasonable suspicion or discrimination in certain contexts, do not inherently lead to constitutional violations unless improperly conducted. Investigating criminal activities, when done lawfully, aligns with the rights of law enforcement and does not typically violate constitutional protections. Therefore, false arrest stands out as a clear example of an action that can directly result in a lawsuit due to its violation of constitutional rights.