Louis was the second son of the Silesian duke Bolesław III the Generous, then ruling over Legnica and Brzeg, and his first wife, the Přemyslid princess Margaret, a daughter of King Wenceslaus II of Bohemia.

Like his elder brother, little was known of Louis I's early years; his first formal appearance was in 1329 on the occasion of the renewal of his father's homage to the Luxembourg king John of Bohemia.

In 1346 Wenceslaus - whose wife, after eight years of marriage was finally expecting their first child - tried to modify the treaty, under which Louis gave up all his lands to his elder brother (who apparently was dying), and in exchange, he was named his sole heir, even in the case of the birth of a son.

The war lasted for nearly six years (with interruptions thanks to the mediation attempts of Duke Konrad I of Oleśnica, of the Bishop of Wroclaw, Preczlaw of Pogarell and Emperor Charles IV himself).

The winner in the conflict was Louis, who in addition to the confirmation of his government over Lubin, obtained from Wenceslas I the town of Chojnów, half of the Oława territory, the Duchy of Brzeg and a monetary compensation of 4,500 pieces of silver.

His talent in government affairs caused Louis I to be actively involved in the rule of Legnica by the request of his eldest nephew Rupert I, who followed most of his advice.

Thanks to the great improvement of the Legnica finances, Louis I was able to retake the half of the Duchy of Brzeg-Oława lost by his late brother (in 1368) and also acquired the towns of Kluczbork, Byczyna, Wołczyn (in 1373) and Niemcza (years 1392–1395).

In order to maintain his sole authority over his lands, despite the attainment of majority of his eldest son Henry VII, Louis I didn't give him a separate state, and only named him co-regent - but without any real power - in 1360 or 1361.

In exchange, the King promised the succession to the whole Duchy of Legnica-Brzeg only to the descendants of Bolesław III the Generous from then on, which saved this line of the House of Piast from further intrusions by their relatives.

A second renewal of homage took place on 6 January 1383, but this time Louis I had to renounce any claims over the duchies whose current holders were relatives of the King of Bohemia: Wroclaw, Schweidnitz and Jawor.