Based on the provided legal document, the key points are as follows:

1. The right to collect river sand from designated portions of rivers within Panchayats is granted through a process of auction conducted by the Panchayats. The highest bidder is awarded the right, which is confirmed in a Panchayat meeting (!) .

2. The auctioned right involves the purchase of a "profit a prendre," which is a benefit arising out of land, and is considered an interest in immovable property. This right includes the authority to remove sand from specific portions of the river, which is attached to the land and thus classified as immovable property under applicable laws (!) (!) (!) .

3. The legal framework, including relevant sections of the Kerala Panchayat Raj Act and the Transfer of Property Act, indicates that such rights are subject to transfer duties and must be executed through registered instruments if their value exceeds certain thresholds. The right to remove sand, being an interest in land, falls within this category (!) (!) (!) .

4. The petitioners' contention that they only purchased a permit and not an interest in immovable property is not supported by legal interpretation. The right to extract sand is akin to a benefit arising out of land, and thus, it is regarded as immovable property, requiring execution of a proper registered agreement on a stamp paper of specified value (5% of the bid amount) (!) (!) (!) .

5. The execution of an agreement on a stamp paper of the specified value is a mandatory legal requirement for the transfer of such rights, and failure to comply with this requirement invalidates the transfer, preventing the petitioners from removing sand (!) (!) .

6. The interpretation of relevant statutes and legal principles confirms that rights to benefit from land, such as the right to remove soil or minerals, are classified as immovable property. Consequently, the provisions of the relevant laws regarding registration and stamp duty apply accordingly (!) (!) (!) (!) (!) (!) .

7. The contention that the right to collect sand does not constitute immovable property is rejected, as the legal definitions and judicial interpretations establish that such rights, being benefits arising out of land, are inherently tied to immovable land and thus subject to the applicable transfer and registration laws (!) (!) (!) .

8. In conclusion, the court finds that the petitioners have purchased a right that qualifies as an interest in immovable property, and therefore, the agreement must be executed on a stamp paper of the prescribed value. The failure to do so results in the invalidity of their claim to remove sand, leading to the dismissal of the petitions (!) (!) (!) (!) .

9. Overall, the legal principles and statutory provisions affirm that rights arising from land, including those to extract minerals or soil, are to be treated as immovable property, and adherence to registration and stamp duty requirements is mandatory for valid transfer or grant of such rights.