To challenge an improper joinder, a lawyer must first identify whether the issue constitutes misjoinder or non-joinder under Rule 21 of the Federal Rules of Civil Procedure or Order I Rule 10 of the Civil Procedure Code, 1908, and gather factual grounds proving that the joined party or claim lacks a legal or factual connection to the case. The lawyer then files a motion to strike or sever, supported by an affidavit or memorandum citing relevant statutes, and serves notice to all parties involved. At the hearing, counsel must demonstrate that correcting the error will ensure judicial efficiency and prevent prejudice, requesting either severance, amendment, or substitution of parties as necessary. Courts generally permit such corrections without dismissing the entire case, provided the motion is timely, legally justified, and aimed at preserving fairness and procedural integrity.