Saint-Gobain does not have to make a public takeover offer before purchasing a controlling interest in the company, the Swiss Administrative Court ruled.
Minority shareholders in Sika, including the Bill and Melinda Gates Foundation Trust, have bitterly fought the takeover bid.
Saint-Gobain agreed to purchase the 16.1 percent stake in Sika held by the Burkard-Schenker family, which founded the company, for 2.75 billion francs ($2.86 billion).
The founding family holds a particularly powerful class of shares.
It means that if Saint-Gobain's purchase of these shares goes through, the French firm would control 52.4 percent of voting rights in Sika.
Sika's minority shareholders have lashed the offer, accused Sika's founding family of disregarding the company's interests and engaged in a protracted battle in court.
They lost that battle on Tuesday, in a decision that Switzerland's Administrative Court said was final and not subject to appeal.
The Gates Foundation Trust, said it would continue to fight to quash the deal.
"The Foundation Trust will continue to defend their shareholder rights and oppose the ill-advised planned transaction that was structured to serve only the interests of Schenker-Winkler Holding AG (the Burkard family) and Saint-Gobain," according to a statement from Cascade Investments and the Gates Foundation Trust.
"The proposed transaction makes no strategic sense, is an affront to good corporate governance and is not in the interest of Sika's business, employees, customers or public bearer shareholders," it said.
"Cascade and the Gates Foundation will continue to protect their investment in Sika and oppose the transaction until reasonableness prevails, even if that requires a multi-year battle."
Saint-Gobain rejects the notion that its offer will be bad for Sika's business, predicting the merger will produce synergies worth roughly €100 million through 2017 and 2018, with larger profits in the future.
Representatives of the Burkard-Schenkers have long insisted that they are entitled to sell their stake at whatever price they deem fair.