I am very sorry to differ. Usually, I don't read other answers. But I wish to clear the issue of what is going on in practice at ground level facts.
The Industrial Standing Orders Act is an old phenomenon. It never stops the principal employer's liability on the welfare of workers, including contract labor who have below 50 or above fifty. These number games are applicable for online payment of license registration and at the time of renewals only. If any accident occurs in a factory where a contract laborer is injured or dies, unfortunately, the principal employer never escapes his liability to pay compensation under the EC (WC) Act. Similarly, all acts of the law of the land are applicable to a factory that has regular or contract labor with a license or not necessary license. Under all labor acts applies there and preferably the principal employer's liability on the safety and welfare of workers working on the company's premises or workers engaged by the company for outside works like marketing and transport. The principal employer never escapes his liability as the owner of the company. When the company is his ownership, all the working force is also his people.
Recently, there was an Ammonia gas leakage in a company where two were affected, unfortunately, one contract laborer died, and one was injured. They were working under a contractor without a necessary license. That factory has standing Industrial orders applicability. However, the labor department issued notices. The principal employer attended the court and paid compensation through his contractor. An IPC case is already registered by the police, and the case is ongoing. So, I think I have cleared your doubts. The principal employer never escapes his liability by showing the Industrial Standing Orders document. No doubt, it is useful for recruitments, disciplinary actions, salary hikes, promotions, union elections, disputes settlements, and a timetable plan of action for the day-to-day running of the factory; it is useful like a manifesto. However, it is not for evading the safety and security of his company workers in any way.
I wish to add one example from a few years back. One factory employer engaged two outside workers to cut overgrown trees 🌲🌳🌴 in his factory. Unfortunately, one worker was injured and later died. The labor department was involved, and the principal employer paid 5 lakhs compensation to the bereaved family. The employer purely personally engaged for a day's work. The employer's liability on safety and welfare remains unaffected, irrespective of applicability under different acts.
Thank you, please 🙏.