A group of Iranian lawmakers has begun drafting a bill on reattaching Azerbaijan to Iran by updating the terms and conditions of a 19th century treaty that ceded part of modern-day Azerbaijan and most of Armenia to Russian control.

The 1828 Turkmenchay Treaty ended the last war between Russia and Persia and paved the way for St. Petersburg to establish suzerainty over the South Caucasus. (Tehran already had given up its claims on Georgia in the 1813 Treaty of Gulistan.)

But the Iranians now argue that there was a critical detail in the fine print.

The treaty, they say, was valid only for 100 years and, therefore, the lawmakers’ logic goes,“re-annexing” Azerbaijan, Iran's northern next-door neighbor, is in order, Iran's government-run FARS news agency reported. Cities "lost" to the Russian Empire were supposed to be returned to Tehran just like "the British-Chinese deal over Hong Kong," the agency claimed.

Politicians in Baku were quick to counter that it is actually Iran that needs to hand over a chunk of its territory to Azerbaijan -- specifically, the northwestern border areas whose primarily ethnic Azeri residents make up about a quarter of Iran's population of roughly 74.8 million.

"Persians have always been in our bondage," asserted ruling Yeni Azerbaijan Party Executive Secretary Siyavush Novruzov, APA news agency reported.

The hostility between Tehran and Baku has been on a low simmer for years, though usually kept on the back burner. Despite periodic attempts at top-level diplomacy, claims to each other's territory, rivalry over Caspian Sea energy resources and alliances with each other’s arch-enemies (Israel and Armenia, respectively) keep the suspicions steadily bubbling.

In March, a group of Azeri Iranians who back secession and possible unification with Azerbaijan gathered in Baku; Tehran responded with a diplomatic note and then dusted off the Turkmenchay Treaty.

Its review, however, does not appear to apply to Iranian ally Armenia, also mentioned in the Turkmenchay Treaty.

In the South Caucasus, where virtually everyone has territorial claims -- stated or muted -- against everyone else, any look back at history can be a highly subjective and perilous exercise.

Both Russia and Iran consider themselves to be the liberators of the Caucasus, while the Caucasus peoples mostly see the two as invaders. So far, none of the countries concerned has learned that such conflicts are better left in the past. It's unlikely that the fight over the Turkmenchay Treaty will prove any different.