Hello Yuuko,
yung squatters sa lupa na minana ni Juan are invoking the Lina Law - eto yun law protecting the rights DAW ng mga squatters..
Si Juan pa rin ang may-ari nung lupa pero di niya basta-basta puede paalisin ang mga squatters without any court order.Kung gusto nyang makuha ang possession ng lupa at mapaalis ang mga squatters, magsasampa siya dapat ng kasong ejectment sa metropolitan trial court nung lugar kung saan located yung lupa tapos hihingi na rin siya sa korte na pabayaran sa kanila yung reasonable na rentals sa paggamit nila ng ilang taon sa lupa niya plus damages at attorney's fees. Under Rules of Summary procedure ang iaapply sa hearing ng kaso ni Juan kaya mabilis ang process nun kumpara sa regular na proceso sa korte.. 
In answering yuuko's query, one question must be answered: How long have the squatters stayed in the lot?
The duration of their stay is very material to the situation at hand.
If the squatters have stayed in the lot for more than a year, laitzu's suggestion will already fail. The Rules of Court provide that in order for the ejectment complaint to proceed, the squatter's possession of the lot should be less than one year. According to the facts of the case, the squatters have been staying there since the time of Juan's grandparents. Thus, an ejectment case against the squatters will not hold water. What Juan should do is file a reivindicatory action to recover ownership of the land.
HOWEVER...
If the squatters has stayed there for more than 30 years or even just a substantial amount of time and held the lot as if they were the real owners of the land, then Juan has a very big problem. This is because the squatters may have already acquired ownership of the land through either acquistive prescription (with regdard to the 30 year period) or laches (with regard to the length of time wherein Juan did not protect his right over the lot). Why does the law allow this? This is because as the owner of the property should readily guard his rights over the property against anyone. Since a substantial period of time has elapsed since the intruders entered into his property and he did nothing, it is as if he relinquishes his rights over his property. In other words, the loss of the property is the owner's fault because he did not protect his rights.
