Final answer:
A lawyer cannot enter into agreements that restrict their right to practice law, which includes ethical obligations ensuring their freedom to practice and uphold the right to an attorney as constitutionally protected by the Sixth Amendment. Cases like Glasser v. United States define conflicts of interest that can impede this right.
Step-by-step explanation:
The question raised concerns the ethical responsibilities of lawyers under professional conduct rules. Specifically, a lawyer is prohibited from entering into an agreement that restricts their right to practice law after terminating a relationship with a client. This is to ensure that lawyers retain the freedom to offer their services to the public without undue restriction.
One of the fundamental principles of legal practice is maintaining the right to an attorney, guaranteed by the Sixth Amendment. In Glasser v. United States, it was established that conflicts of interest, such as those created by simultaneous representation of co-defendants, are a violation of this right. The assistance of counsel clause ensures the accused has access to unfettered legal defense.
Furthermore, ethical guidelines imply there can be no additional restrictions that legally restrict others from doing anything the license permits. Lawyers have the duty to offer services without being bound to future limitations on their career movements or practice capabilities, which could undermine their professional obligations or availability to serve the public interest.