Short answer. No. Article 1646 extends the disqualifications in Articles 1490 and 1491 to leases, not just sales. Since Article 1491 bars lawyers from acquiring property that is the object of litigation they handle, that same lawyer is also disqualified from becoming the lessee of that property while the case is pending.
What the law says
The persons disqualified to buy referred to in articles 1490 and 1491, are also disqualified to become lessees of the things mentioned therein.
Civil Code, Article 1646 — Who Cannot Be a Lessee. Read the full provision →
A Sales Rule Borrowed for Leases
Articles 1490 and 1491 list persons barred from buying certain property because of a conflict of interest: spouses buying from each other, guardians buying a ward's property, agents buying what they were told to sell, and lawyers acquiring property involved in litigation they are handling. Article 1646 simply extends every one of those same disqualifications to leasing, not only to buying.
How It Reaches a Lawyer
Article 1491 disqualifies lawyers from acquiring, by purchase or assignment, property that is the object of litigation in which they take part by reason of their profession. Because Article 1646 pulls that same restriction into leases, a lawyer cannot lawfully become the lessee of the very property under litigation he is representing a client on, even if the lease looks like an ordinary rental arrangement.
What Happens If the Lease Goes Through Anyway
A lease entered into in violation of this disqualification is treated the same way the law treats a prohibited sale under Articles 1490 and 1491: it is void, because the prohibition exists to prevent a professional from using his position or access to influence or exploit the very property or client relationship in front of him, regardless of whether either party acted in good faith when the arrangement was made. Beyond the civil nullity, a lawyer who does this also risks professional discipline under the Code of Professional Responsibility, since the same conduct that voids the lease is independently a breach of the fiduciary duty owed to a client.
Beyond Lawyers
The same rule reaches other disqualified persons acting in the same roles Articles 1490 and 1491 name, including guardians as to a ward's property, agents as to property they were authorized to manage or sell, executors and administrators as to estate property under their charge, and public officers and employees as to property whose administration has been entrusted to them, so the restriction is not limited to the legal profession even though lawyers are usually the clearest example. The disqualification does not reach a lawyer's relatives or law partners merely by association, and it stops applying once the litigation the property is tied to has been finally resolved, since the conflict of interest the rule guards against no longer exists at that point.