It is considered legacy resource those allocated before RIRs (Regional Internet Registry) formation.
Any Internet Resource (IP block, ASN) with registration date before Dec 28th 1997 is considered legacy. With the formation of RIRs, the Internet Resources started to be allocated by these organizations.
This differentiation is important because after its formation, each RIR started to implement and utilize its own regional policy to allocated Internet Resources. Those policies aimed to better answer particular needs of each region.
Resources allocated after the mentioned date follow the existent policies which were suggested and approved by the community in each region. These resources are subjected to allocation fees and also renewal or maintenance fee. Also, organizations that receive resources from RIRs are, in most of the cases, members of these RIRs.
Regarding to LACNIC, every organization that receives IP block allocation is member of LACNIC. And so, are entitled to attend meetings and training organized by LACNIC, to elect board members and also to be part of LACNIC board.
Organizations that have received legacy resources can also became LACNIC member. To do so, they have to fill up the application form and pay the member registration fee. Details can be found at this link.
The transfer of legacy resource from one organization that has its custodian to other is possible only in the cases when the transfer is result of a legal operation which can be audited by appropriate documentation. Details can be found at this link.
Transfered Legacy resources will no longer be considered legacy after the transfer and the organization that received its custodian will became LACNIC member when the transfered resource is an IP block. The transfered resource will be subject to effective renewal or maintenance fee.
Organizations that has legacy IP block custodian can request additional IP blocks, therefore, contiguous block can not be assured.
Once an additional block allocation is approved, all previous blocks will no longer be considered legacy. In this case, the organization will became LACNIC member and will be subject to effective IP blocks renewal fee. The organization category will be calculated considering all previous blocks and the additional one.
Legacy resources are being transfered from a central registry to the appropriate RIRs.
This transfer follows an time schedule elaborated by the RIRs and can be checked at this link.